2G - The network with the lowest speed. Theortical max of ~6KB/sec.
EDGE - 2.5G. Adds sprokets, dongles, and widgets to boost the theoretical max speed to 128KB/sec.
3G - Your standatd 3G network. Has a theorectical max of 6.1MB/sec.
HSPA - 3.5G network. Improved discombobulators increase your theoretical max speed to 1.8MB/sec down and ~729KB/sec up.
HSPA+ - A seriously speedy 3.5G network. Improved calibration techniques increase the theoretical max to 21MB/sec down and 2.75MB/sec up.
LTE - A rocket speed 4G network. Attaching rocket boosters to your device catapults your theoretical max speeds to 12.5MB/sec when moving or 128MB/sec when stationary.
Note that this information is not guaranteed to be accurate! It is the result of a quick 5 minute research session thrown together in order to help people identify which mobile network is which.